power antenna question

[GNRick]

I replaced my broken antenna in my 87 GN with a GM factory new one. Found it on E-bay. Antenna goes up with hot lead from battery, so I know the motor works. However, it won't go down. When I energized the blue wire going to the wiring harness behind the radio, I get a click from the black relay behind the glove box. Keeping the blue wire energized, I tested the 3 wires in the harness at the antenna. My test light lights up hot for the green wire, and also indicates the grey wire is the ground. However, I can't get anything from the white wire. It appears to be neither hot nor ground. What should the white wire do? I also tested it at the relay, and still nothing. Does this mean the relay is bad? If so, are they still available from GM? Thanks!